A cyclist who stumbled across the French Alps massacre has described finding "heads with bullet holes in them" in a scene reminiscent of a Hollywood film.

Brett Martin likened the carnage in the secluded car park to a set from TV crime series CSI Miami as the man leading the investigation said the clue to the four murders lay in Britain.

Mr Martin was the first witness to arrive at the spot where engineer Saad al-Hilli, 50, his dentist wife Iqbal, 47, and her elderly mother were blasted to death at the top of a hill in the Combe d'Ire forest, near Chevaline.

Speaking for the first time, he told how he found the al-Hillis' daughter Zainab, seven, "stumbling" around, bleeding and "moaning", close to the family car. Mr Martin has been credited for potentially saving Zainab's life. The child, who was shot in the shoulder and badly beaten around the head, is now recovering in hospital.

Next to the BMW lay the body of Sylvain Mollier, 45, a French cyclist who apparently stumbled across the attack. The wheels of the vehicle itself were still spinning and its engine was revving. Inside, Mr Martin made out three bodies.

"It was pretty much what you would imagine a set from (TV crime series) CSI Miami would be like," he told the BBC. "There was a lot of blood and heads with bullet holes in them."

He added: "I've never seen people who have been shot before... it seemed to me just like a Hollywood scene and if someone had said 'cut' and everyone had walked away, that would have been it. But unfortunately it was real life. It became quite obvious, now, taking stock, that it was a gun crime."

After checking on the bodies in the car, Mr Martin said there was no sign of the al-Hillis' younger daughter Zeena, four, who had been cowering underneath her mother's body during the brutal attack.

His recollection of events emerged as Annecy's chief prosecutor Eric Maillaud met his British counterparts working on the case at the al-Hilli family home in Claygate, Surrey. Mr Maillaud - who was accompanied by examining magistrate Michel Mollin, another senior member of the inquiry team - said it was "without any doubt that the reasons and causes (for the killings) have their origins in this country".

Police have revealed they are probing three lines of inquiry, focusing on Mr al-Hilli's work, his family and links to his native Iraq. The aerospace engineer had been holidaying with his relatives at a campsite near Lake Annecy when they were attacked at 4pm last Wednesday. Surrey Police later said they had held an "extremely productive" meeting with senior Gendarmerie officers, the Crown Prosecution Service and a French prosecutor and judge leading the investigation.